(nitpicking alert)

The docs for encoding/gob says "Maps are sent as an unsigned count followed by that many key, element pairs. Empty but non-nil maps are sent, so if the sender has allocated a map, the receiver will allocate a map even if no elements are transmitted."

It is not mentioned explicitly, but what if the encoder encodes a nil map, will the decoder create a new map?

http://play.golang.org/p/U3QI5MW5fV

The test shows that it will, so the docs should probably be updated to drop the "Empty but non-nil maps
are sent...". In fact, nil maps and empty but non-nil maps are not differentiable.

/cc @robpike